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William H. Wilson IV
Emily Heeb
William Bowlus
Andy Jetter
Stephen Nelson
Crystal Barron
Biomedical Engineering
Biomedical Engineering
Biomedical Engineering
Biomedical Engineering
Industrial Design
Nursing
Design a cerebrospinal fluid collecting device to be used in under resourced environments by personnel with minimal training
Current difficulties of procedure:◦ Finding insertion location
◦ Determining insertion depth
22g Whitacre NeedleProvides access to dura while causing minimal trauma. Reduces post-puncture headache.
Usability Testing◦ Cadaver Labs
◦ Tissue Coring Test
◦ User Drape Studies
Fluid Flow Analysis
Device Failure analysis◦ Mechanical Failure
◦ AFMEA
Cadaver Lab◦ Test overall usability of device◦ Cadaver tissue too rigid for assessment
of functionality
Tissue Coring Test◦ Investigated if a whitacre (bullet tip)
needle will core tissue as it is advanced into the spinal column
◦ Tests performed on porcine tissue◦ The whitacre needle did not core tissue
while being advanced
Assess fluid flow through various needles◦ Determine time to visual
CSF flow.
Results◦ 18 Gage Quinke - 1 mL / 14 sec
◦ 22 Gage Quinke - 1 mL / 2.0 minutes
◦ 25 Gage Whitacre - 1 mL / 7.9 minutes
◦ CSF fluid in flash chamber - < 1 sec
To assess the drape’s ability to properly locate the L4-L5 vertebral space
Study performed by untrained users◦ Nursing and Biomedical Engineering
Students
Results – Round 1◦ First Generation Drape Average X deviation 1.10 cm Average Y deviation 4.84 cm
◦ Drape did not meet horizontal or vertical accuracy specification
Results – Round 2◦ Second Generation Drape
Average X deviation 0.80 cm
Average Y deviation 1.42 cm
◦ Better accuracy when applied to patient lying down
◦ Drape met horizontal accuracy specification
More work needed on vertical accuracy
Application Failure Modes and Effects Analysis (aFMEA)
High Risk of Bumping the System while inserted in patient
Possible design control: Adhesive securing disc
Sufficient thread lubrication is imperative
Likelihood of user impatience while unscrewing the dial Possible design control: Quick release feature
Likelihood of sterility compromise Possible design control: Training supplement, significant
emphasis in IFU
Whitacre Needle Buckling◦ Critical Buckling Force = 5 lbf
◦ Insertion Force = 2.25 lbf
Introducer most susceptible:◦ Flange Bending Break
◦ Threaded Shaft Bending Break
◦ Threaded Shaft Torsion Break
Flange Bending Break◦ Utilized simple model to replicate a worse scenario
◦ Stress ≈ 700 psi
Threaded Shaft Bending Break◦ Force applied at tip of shaft = 4 lbf
◦ Stress ≈ 2,700 psi
Threaded Shaft Torsion Break◦ For Torque = 15 lbf in
◦ Shear Stress ≈ 2,250 psi
Material Yield Stress ≥ 3,000 psi
Material Yield Stress ≥ 3,000 psi
Minimized cost◦ High importance for device success in target demographic
Injection Molding compatible
Durable
Two types of polypropylene are top choices
◦ Polypropylene (50% Glass Fiber Filler)
Better Mechanical Properties
More Expensive
Opaque
◦ Polypropylene (Copolymer, UV Stabilized)
Translucent
Cheaper
Acceptable Mechanical Properties
Polypropylene (copolymer, UV stabilized) ◦ Yield strength ≈ 3,670 psi
◦ Bulk cost ≈ $1.00/lb
◦ UV Radiation Durability: Good
Next Steps◦ Additional tests to verify mechanical stability
◦ Investigate costs involved with manufacturing processing
Injection Molds, etc.
◦ Sterilization investigation
Finalization of needle design◦ Investigating Additional features
Quick Release of threads
Relative rotation for knob
Securing disc to skin
Revision of drape◦ Still need to meet vertical accuracy requirement
◦ Refinement of application procedure
◦ Layout of alignment features
Verification and Validation
◦ Clinical Efficacy
Porcine model
Clinical trials
◦ Production Trials
Testing on manufactured prototypes
◦ Durability testing: aging, drop testing, etc.
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